Sniper teams typically include two members. The first is the sniper, who physically wields the weapon. The second is a spotter, who provides situational information to the spotter. The spotter is typically responsible for monitoring environmental conditions such as wind speed(s) and temperature, for example, as well as the range to the target and any other information that may effect the trajectory of the projectile as it proceeds toward the target.
Referring to FIG. 1, a basic sniper rifle 100 is shown. The sniper rifle 100 includes a weapon 102 and a telescope 104, commonly called a “scope”. The weapon 102 is the actual “gun” that fires the bullet. The scope 104 is typically an adjustable magnifying optical system to isolate targets of interest. The internal optics of the scope generally provide a physical reticle 106 that is typically etched in glass in the optical path of the scope 104. Often, the physical reticle 106 is a simple a cross hair with markers. For sake of brevity, further discussion focuses on the cross hairs with markers, although any shape can be equivalently used.
The scope 104 is adjustably connected to the weapon 102. As discussed more fully below, on occasion a sniper may need to adjust the position of the scope 104 relative to the weapon 102. This movement is generally achieved by a variety of knobs 112 located along the outer periphery of scope 104. One such knob 112 will typically control the “elevation” of the scope 104, which causes the scope 104 to rotate around its X-Z axis to account for up/down changes relative to target. Another such knob 112 will typically control the “windage” of the scope 104, which causes the scope 104 to rotate around the X-Y axis to account for left/right changes relative to target. A third knob 112 will typically control “parallax” of the scope 104, which raises and lowers the scope 104 in the z-x plane. Additional knobs, buttons and/or other controls may also be provided for focus, magnification, aperture control, and/or the like.
All of the knobs 112 generally have specific set positions that will “click” when the knob is moved into that position. Although the knobs could be adjusted by sight, in practice the “click” provides a tactical response that allows the sniper to adjust the knob settings via touch without having to take his or her eye off the target. The adjustment that results from knob rotation of a single “click” is usually consistent with a one hash-mark change in the reticle 106. Thus, by way of non-limiting example and referring to FIG. 2, a one click rotation to the left would adjust the scope 104 such that the optical path would shift by one hash-mark to the left (replacing B in the center of the reticle with A).
Sniper rifle 100 is initially calibrated through a process often referred to as “zeroing the reticle.” The goal is to align the center of the reticle 106 with the boresight of the weapon 102 (a straight line trajectory between the weapon 102 and the target). Generally speaking, the sniper wants the bullet to penetrate a target at exactly the dead center of reticle 106 under ideal conditions.
The sniper brings the rifle 100 to a controlled environment with zero elevation and zero lateral movement, sets the target at a distance at which vertical drop of the bullet due to gravity is not a factor, aligns the center of the reticle 106 with the target, and fires. If the scope 104 is in proper alignment with the weapon 102, the bullet will strike the target at the dead center of the reticle 106. If the bullet strikes somewhere else, then the weapon 102 is out of alignment with scope 104; the sniper adjusts the position of the scope 104 by adjusting the knobs 112 and repeats the process until proper alignment is achieved.
Despite what is now near-perfect alignment of the sniper rifle 100, when used in distances common for sniper conditions (e.g., typically on the order of 300 meters or more for military use) the bullet is nevertheless unlikely to strike the target as centered in the reticle 106 due to a variety of conditions that can effect the movement of the bullet over such large distances. Such conditions include, for example, wind, humidity, temperature, gravity and the like. Wind can be a particularly influential condition that can change rapidly and radically. Additionally, weapon and ballistics conditions such as the size, shape, velocity, mass and/or temperature of the bullet can affect the travel of the bullet.
The role of the spotter, then, is to account for as many of these conditions as possible and to evaluate, as best possible, what adjustments can to be made to the sniper's aim to compensate. That is, the spotter's job is typically to determine the optimum deviation from the boresight of the sniper's weapon 102 to increase accuracy. To illustrate, FIG. 3A shows one example in which the sniper aligns the reticle 106 with the target 302. The spotter determines, for example, that because of extreme distance to the target the bullet will drop due to gravity such that the sniper's current aim is too low by two hash marks. The spotter in this instance also determines that a left-to-right wind will push the bullet to the right such that the sniper's aim is too far to the right by two hash marks. Due to these conditions, the bullet fired as shown in the example of FIG. 3A would strike the area shown by dot 304, missing the target.
To compensate for these conditions, the spotter would typically communicate to the sniper to adjust the aim of the rifle up and to the left by two hash marks in each direction, essentially centering the reticle 106 on the “B” location as shown in FIG. 3B. The sniper then fires; if the calculations are correct and no other adverse conditions are in play, the bullet aimed at point B in the scope 104 should drop due to gravity and move to the right via wind to strike the target 302, thereby making a hole 304 dead center in the target 302. Similar concepts could be applied to any number of other examples relating to any number of compensatable factors.
A complicating factor in the spotter's calculations is to take into account the current position of the scope 104, which may (or may not) have been adjusted since it was first aligned. As noted above, conventional scope adjustments are relative rather than absolute. More specifically, there is not presently any absolute position (e.g., geographic position, such as GPS coordinates) that the spotter calculates. Rather, scope compensation is based on the position of the scope 104 relative to the necessary correction. The spotter and/or sniper therefore needs to know how the scope 104 is currently positioned so that information can be used in determining how to compensate for the proper offset.
In practice, the sniper team generally uses a specific pre-agreed upon vocabulary to communicate compensation information between the spotter and the sniper, often in units of “clicks” that correspond to movements of knobs 112 of the scope 104. For example, the sniper can communicate current scope orientation as “one-click left, four-clicks up” or “−1 windage, +4 elevation” to inform the spotter as to the current orientation of the scope 104 relative to the zero alignment. The spotter then calculates how the sniper should adjust his or her weapon to compensate for the shot; for example, the spotter may say “one click to the left, three clicks down.” In the example illustrated in FIG. 3, the offset “B” is to the upper left, so the spotter may relay compensation data such as “2 clicks left, 2 clicks up” to the sniper.
The sniper will typically respond to this compensation data in one of two ways corresponding to either (1) movement of the weapon 102 or (2) readjustment of the scope 104. The first method, as shown in FIG. 3A-C, would be for the sniper to simply adjust the angle of the rifle to align the cross hairs by the desired amount. In the example of FIG. 3B, the sniper intending to hit point “A” would move the weapon so that reticle centers on point “B”. The sniper then fires; if the compensation data was accurately calculated and applied, the bullet may (as discussed below) strike target 302, as shown by hole 304. An advantage of this method is that the sniper does not change the scope 104 from its calibrated alignment. A disadvantage is that the sniper takes the reticle off the target and “eyeballs” how to realign his weapon to make the correction per the number of clicks. That is, the sniper does not aim directly at the target, thereby inherently leading to imprecision.
The second method of responding to compensation data would be for the sniper to physically adjust the scope 104 by turning the knobs 112 by the amount instructed by the spotter. An advantage of re-orienting the scope 104 with respect to the weapon is that the reticle 106 will then be directly over the target 302 when the shot is taken. The disadvantage, however, is the weapon is now out of its original alignment. This deviation from the original alignment would need to be considered for subsequent shots until the scope 104 is restored to its default setting at a later time.
Despite the best efforts of the sniper and spotter, shots can still miss due to environmental effects, errors, and/or other factors. Environmental factors refers to undetected factors that could not be properly accounted for in the spotter's calculations. Wind conditions proximate to the target, for example, could be significantly different from those measured at the spotter's location. The target could also be behind a certain type of glass or other barrier that alters the angle of the bullet. Any number of other environmental effects could alternately or additionally be present.
Inaccuracy also results from imprecision or other error. Errors could arise for any number of practical factors including: error in communication/tracking of the actual position of the scope 104; error in the calculation of the number of clicks needed; error by the sniper in applying the clicks; latency, and/or the like. Latency can occur during the few seconds between the spotter providing the compensation information and the spotter firing the shot, during which time external conditions may already have changed such that the prior calculations are outdated. The impact of such errors in best viewed in context: the desired location of a sniper shots may be the target's chest, which is usually an area roughly 10-14 inches wide. But for a sniper shot at 2500 meters, a one click “error” would translate into a roughly 10 inch deviation off the desired target point, corresponding to almost a full body width. Even the smallest error can thus be the difference between hitting and missing the target. In this context, the term “error” is used to refer to any sort of human inaccuracy that is inevitably present in any situation. The use of the term is by no means intended to disparage the fine efforts or work of American servicemen. Indeed, a lethal hit on the first bullet is considered unlikely in practice due to the frequency and impact of environment and error.
When the first shot misses, however, the sniper can usually see where the bullet strikes. The distance between the impact point and the target point provides the sniper with an instantaneous second set of compensation data that allows for an improved second shot. The split-second nature of this circumstance, however, generally dictates that the second shot be taken with the first method above (weapon 102 realignment) rather than the second method (scope 104 realignment).
The above methodology can have various drawbacks. As noted above with respect to the missed shot, the process allows for human error in determining, communicating and/or applying compensation data. The information is also communicated orally, thereby creating latency and increasing the probability of detection.
Research is underway to design equipment that would more automatically and efficiently perform the compensation calculation and provide corresponding compensation data. However, no technique or system currently exists for the spotter and sniper to exchange the information discussed above in a meaningful way that avoids various drawbacks. These and other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background section.